Scavenger compositions for sulfur species

ABSTRACT

A scavenger composition comprising a carrier and an active metal, wherein the carrier is present in an amount of about 1.0 wt % to about 99.0 wt. %, based on total weight of the composition, and the active metal is present in an amount of about 1.0 wt % to about 99.0 wt. %, based on total weight of the composition, wherein the active metal is a metal salt or metal chelate, and wherein the metal is chosen from iron, copper, molybdenum and zinc.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.16/067,888 filed 3 Jul. 2018, which is a 371 National Stage entry ofInternational Application No. PCT/US2017/012468 filed 6 Jan. 2017, whichclaims priority to U.S. Application No. 62/276,472 filed 8 Jan. 2016,the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention is directed towards scavenger compositions forinactivating at least one sulfur species. More particularly, the presentinvention relates to hydrogen sulfide scavengers additives for asphalt.

According to the American Society of Testing Material (‘ATSM’), asphaltis defined as “a dark brown to black cementitious material in which thepredominant constituents are bitumens which occur in nature or areobtained in the petroleum processing” (i.e., obtained by fractionaldistillation of petroleum). In industry, the terms asphalt and bitumenare used interchangeably, with asphalt more commonly used in the UnitedStates, and bitumen more commonly used outside the United States. Forthe purpose of the present application, as well as for clarity, the termbitumen is used to refer to the ‘dark brown to black cementitiousmaterial’, while asphalt is used to refer to asphalt concrete or asphaltcement; that is, the combination of at least bitumen and aggregates.

Bitumen used in forming asphalt is available in different grades,depending upon the source of the crude oil from which the bitumen isderived. Further, there are various ways to grade bitumen, such aspenetration grading, viscosity grading and performance grading. Forpenetration grading, bitumen is classified by the depth to which astandard needle penetrates the bitumen under specified test conditions.This needle test characterization indicates the hardness of bitumen,with a lower penetration indicating a harder bitumen. Specifications forpenetration graded bitumen normally state the penetration range for agrade (e.g., 50/70). Viscosity graded bitumens are graded and specifiedby their viscosity at a standard temperature (typically 135° C.).Specifications for viscosity graded bitumen normally give the nominalviscosity preceded by a V (e.g. V1500). Unfortunately, penetration andviscosity grading are somewhat limited in their ability to fullycharacterize bitumen for use in hot mixture asphalt (‘HMA’) pavement.

Performance grading incorporates tests and specifications that moreaccurately and fully characterize bitumen for use in HMA pavements. Forbitumen, this involves expected climatic conditions as well as agingconsiderations. Like the penetration and viscosity grading systems,performance grading uses a common battery of tests, yet also specifiesthat a particular bitumen must pass these tests at specific temperaturesthat are dependent upon specific climatic conditions in the area of use.Performance grading is reported using two numbers—the first being theaverage seven-day maximum pavement temperature (° C.) and the secondbeing the minimum pavement design temperature likely to be experienced(° C.). For example, a performance grade (‘PG’) 58-28 bitumen isintended for use where the average seven-day maximum temperature is 58°C. and the expected minimum pavement temperature is −28° C. As a generalrule, performance grade bitumen that differ in the high and lowtemperature specification by 90° C. or more typically require some sortof modification.

Modified bitumens are bituminous binders whose performance properties(e.g., elasticity, adhesive or cohesive strength) have been modified byone or more additives. These additives include fillers, extenders,polymers, oxidants, rejuvenators, antioxidants, antistripping agents,waste materials (e.g., crumb rubber) and polyphosphoric acid, amongothers.

Asphalts often require modification in order to meet specifications.Additives can be added to the bitumen or asphalt to aid it in meetingthose specifications. In this respect, various types of additives can beadded to meet different types of improvements. These improvementsinclude lower stiffness (or viscosity) at the high temperaturesassociated with construction in order to facilitate pumping of theliquid bitumen, as well as mixing and compaction of HMA; higherstiffness at high service temperatures for reducing rutting and shoving;lower stiffness and faster relaxation properties at low servicetemperatures in order to reduce thermal cracking; and increased adhesionbetween the bitumen and the aggregate in the presence of moisture toreduce the likelihood of stripping (i.e., the separation of the bitumenfrom the aggregate).

Modifiers include various types of polymers that can be added to thebitumen to increase HMA stiffness at high service temperatures, increaseHMA elasticity at medium service temperatures to resist fatiguecracking, or decrease HMA stiffness at low temperatures to resistthermal cracking. Antistripping agents can be added to the bitumen orasphalt to minimize stripping of bitumen from aggregates. Extenders canbe added as a substitute for a portion of the bitumen to decrease aportion of the bitumen required, for example, when recycling asphalt.

Often the bitumen that an asphalt producer receives does not meet theperformance grade required for the location in which the asphalt is tobe laid. For example, the bitumen available to the producer may be PG64-22 bitumen suitable for normal traffic, but regulations or geographyrequires PG 70-22 bitumen for slower heavy traffic, or even a PG 76-22bitumen for heavy standing or interstate conditions. In order to meetthe required grade, the bitumen can be chemically modified by adding anappropriate amount of polyphosphoric acid (‘PPA’). This PPA modificationimproves the high temperature rheological properties of the bitumenwithout affecting its low temperature rheological properties (i.e., thePPA addition increases the average 7-day maximum temperature from 64 to70 or higher, depending on the amount of PPA added, while the minimumtemperature remains the same). Addition of the PPA can also increase thestiffness of the bitumen, depending on the source of the bitumen.

Most bitumens contain organosulfur compounds, resulting in an overallsulfur content of up to 4% of the bitumen. As the bitumen is heated,sulfur is released from the bitumen in the form of hydrogen sulfide(H₂S) or other volatile sulfur compounds (e.g., mercaptans). Hydrogensulfide emissions are regulated so as to limit operational exposure forhealth and safety reasons. Therefore, there is a need to limit theamount of H₂S emitted from bitumen in the processing of asphalt throughboth engineering and/or chemical controls.

SUMMARY OF THE INVENTION

Disclosed herein is a scavenger composition for reducing hydrogensulfide emissions from asphalt comprising a carrier in an amount ofabout 1.0 wt % to about 99.0 wt. %, based on total weight of thecomposition, and an active metal in an amount of about 99.0 wt % toabout 1.0 wt. %, based on total weight of the composition. The activemetal is a metal salt or metal chelate, and is chosen from iron, copper,molybdenum, nickel and zinc.

In certain embodiments, the scavenger composition can further include asuspension aid in an amount of about 0.01 wt % to about 10.0 wt. %,based on total weight of the composition, and a dispersant in an amountof about 0.01 wt % to about 10.0 wt. %, based on total weight of thecomposition. As not all active metals are readily suspendable in thecarrier in and of itself, the addition of the suspension aid anddispersant is advantageous in producing a stable suspension of theactive metal in the carrier.

The active metal is typically in powdered form having a diameter ofabout 100 microns or less. Preferably, the active metal has a diameterof about 20 microns or less.

As noted above, the active metal is a metal salt or metal chelate, andis chosen from iron, copper, molybdenum, nickel and zinc. Examples ofsuch suitable active metal include copper aspartate; copper carbonate;copper citrate; copper gluconate; copper bis-glycinate; copper oxides;copper oxalate; copper sulfate; iron aspartate; iron bis-glycine; ironcitrate; iron fumarate; iron gluconate; iron bis-glycinate; ironsulfate; molybdenum aspartate; molybdenum bis-glycine; molybdenumcitrate; molybdenum fumarate; molybdenum gluconate; molybdenumglycinate; molybdenum sulfate; nickel aspartate; nickel bis-glycine;nickel citrate; nickel fumarate; nickel gluconate; nickel bis-glycinate;nickel sulfate; zinc acetate; zinc arginate; zinc ascorbate; zincaspartate; zinc carboxylate; zinc gluconate; zinc bis-glycinate; zincmethionate; zinc oxide; zinc picolinate; and zinc sulfate. In certainembodiments, the active metal is a copper-based active metal.

The present invention is further directed towards bitumen or asphaltcomprising the scavenger composition described herein. In certainembodiments, the bitumen or asphalt is modified with one or moreadditives. When the bitumen or asphalt is modified with polyphosphoricacid, the active metal is preferably a copper-based active metal.

When the bitumen or asphalt is modified with the scavenger compositionand heated to 100° C. or greater, particularly 130° C. or greater,hydrogen sulfide emissions from the bitumen or asphalt are reduced toabout 10 ppm or less,

Further described herein is a process for preparing a scavengercomposition comprising adding to a carrier an active metal in a ratio offrom about 1.0:4.0 to about 4.0:1.0 carrier to active metal, wherein theactive metal is a metal salt or metal chelate chosen from iron, copper,molybdenum, nickel and zinc, and wherein the scavenger composition isable to reduce hydrogen sulfide emissions,

Because the active metal is typically in powder form, one or more of theactive metals when added to the carrier may settle out. Therefore, incertain embodiments wherein when the active metal is not able to remainsuspended in the carrier, the process further comprises adding to thecarrier a suspension aid in an amount of about 0.01 wt % to about 10.0wt % and a dispersant in an amount of about 0.01 wt % to about 10.0 wt%, based on total weight of the composition, wherein the suspension aidand dispersant are able to provide a stable suspension of the activemetal in the carrier. Preferably the suspension aid and dispersant areadded to the carrier prior to adding the active metal.

The present invention further provides a process for reducing hydrogensulfide emissions from asphalt or bitumen comprising adding to theasphalt or bitumen the scavenger composition described herein. In thoseembodiments where the bitumen or asphalt is further modified withpolyphosphoric acid, the active metal is preferably a copper-basedactive metal.

DETAILED DESCRIPTION OF THE INVENTION

Disclosed herein is a composition in the form of a suspension,dispersion or slurry that is useful as a hydrogen sulfide (H₂S)scavenger. As used herein the terms slurry, dispersion and suspensioncan be used interchangeably. The present invention can be used withmultiple substances, most preferably bitumen or asphalt, to provide thebenefits of a hydrogen sulfide scavenger, as well as improved rheologyof the substance to which it is added (e.g., asphalt containing thesuspension). The scavenger composition or suspension or slurry furtherprovides the ability to add polyphosphoric acid (‘PPA’) and/or theslurry at any point in the asphalt supply chain (i.e., from asphaltpreparation at the refinery up to asphalt application and final use).

Examples of points of addition of the scavenger composition in theasphalt supply chain include, both inline and hatch blending—

-   -   1) Bitumen discharge line from a refinery to storage tank.    -   2) Refinery storage tank to railcar, truck, or barge.    -   3) Bitumen discharge line from railcar, truck, or barge to        storage tank.    -   4) Any point from storage tank and polymer and/or sulfur        injection lines to final destination (tank, truck, barge).    -   5) Any point from storage tank and PPA injection point to final        destination (tank, truck, barge).    -   6) The creation of a scavenger/bitumen concentrate to let down        into un-scavenged bitumen.    -   7) Direct addition to storage tank, truck, barge with or without        mixing capabilities.    -   8) Addition at either the positive or negative pressure points        of an injection line.

The scavenger composition according to the present invention iscomprised of a suspension media or carrier, a suspension aid, adispersant, and an active metal in the form of a metal salt or metalchelate. The composition according to the present invention can be usedwith a variety of substances—preferably asphalt—to act as a hydrogensulfide scavenger and improve the rheology of the substance to which itis added. Further, when used in asphalt modified with polyphosphoricacid (‘PPA’), the scavenger composition is compatible with suchPPA-modified asphalt and allows for the addition of the PPA and/or thecomposition at any point in the asphalt supply chain (e.g., from asphaltpreparation at the refinery up to asphalt application and use).

Suspension medias or carriers useful in the composition of the presentinvention include glycerol, polypropylene glycol, polyethylene glycol,white mineral oil, mineral spirits (e.g., petroleum hydrocarbonsolvent), hydrotreated light petroleum distillate, white spirits,Stoddard solvent, aliphatic naphtha with a flash point (‘FP’) of about38-42° C., odorless mineral spirits (e.g., naphtha (petroleum), heavyalkylate with PP of about 43° C.), and hydrotreated heavy petroleumdistillate (e.g., C₁₁-C₁₃ isoparaffinic liquid with flash point>about61° C.). The suspension media is typically present in the composition inan amount of about 1.0 to about 99.0 wt %, based on total weight of thecomposition, more typically in an amount of about 30.0 to about 80.0 wt%, and even more typically in an amount of about 40.0 to about 60.0 wt%.

Because one or more of the metal salts or metal chelates have apropensity to settle in one or more of the suspension media, thescavenger composition can also include a suspension aid or rheologymodifier to suspend the active metal in the carrier. Examples ofsuitable suspension aids include polysaccharides such as Xanthan or guargum (including anionic, hydrophobic and/or cationic modifiedpolysaccharides), fumed silica, modified bentonite (montmorillonite),hectorites, castor oil derivatives (e.g., polyamide modifiedderivatives), polyamides and modified polyamides, and polyolefins andmodified polyolefins. Also useful are polymers such as polyacrylatesthat have thickening properties. When used, the suspension aid istypically present in the composition in an amount of about 0.01 to about10.0 wt %, based on total weight of the composition, more typically inan amount of about 0.01 to about 5.0 wt %, and even more typically in anamount of about 0.01 to about 2.0 wt %.

In addition to the carrier and suspension aid, the scavenger compositionaccording to the invention includes a dispersant or wetting agent.Useful dispersants include sodium acid pyrophosphate, sodiumpolysulfonate (e.g., sodium poly-naphthalene sulfonate and sodiumpotassium poly-naphthalene sulfonate), sodium alkyl sulfosuccinate, soylecithin (phospholipid), hydroxyl-functional carboxylic acid esters,salts of unsaturated polyamine amides and lower molecular weight acidicpolyesters, and alkyl amine sulfonates (e.g., isopropylaminedodecylbenzene sulfonate). When present, the dispersant is typicallypresent in the composition in an amount of about 0.01 to about 10.0 wt%, based on total weight of the composition, more typically in an amountof about 0.01 to about 5.0 wt %, and even more typically in an amount ofabout 0.01 to about 2.0 wt %.

Active metals useful in the present invention include metal salts andmetal chelates able to reduce or prevent or trap the formation ofhydrogen sulfide from organosulfur compounds. The active metal istypically present in the composition in an amount of about 1.0 to about99.0 wt %, based on total weight of the composition, more typically inan amount of about 20.0 to about 70.0 wt %, and even more typically inan amount of about 40.0 to about 60.0 wt %. These active metals come ina variety of particle sizes and shapes. So that the active metal isbetter suspended in the carrier, it is preferred that the active metalparticle or powder is smaller in size, for example, about 100 microns orless in diameter, preferably about 20 microns or less. The ratio ofactive metal to carrier can be from about 1.0:4.0 to about 4.0:1.0, moretypically from. about 1.5:3.5 to about 3.5:1.5, and even more typicallyfrom about 2.0:3.0 to about 3.0:2.0.

Examples of active metals (both salts and chelates) useful in scavengercompositions according to the invention include iron, copper, molybdenumand zinc salts and chelates of carboxylates, amino polycarboxylates(e.g., EDTA and glycine), phosphates, sulfates and oxides (e.g., I, II,III or IV). These include, for example, copper aspartate; coppercarbonate; copper citrate; copper gluconate; copper bis-glycinate;copper oxides (e.g., I and II); copper oxalate; copper sulfate; ironaspartate; iron bis-glycine; iron citrate; iron fumarate; irongluconate; iron bis-glycinate; iron sulfate; molybdenum aspartate;molybdenum bis-glycine; molybdenum citrate; molybdenum fumarate;molybdenum gluconate; molybdenum glycinate; molybdenum sulfate; nickelaspartate; nickel bis-glycine; nickel citrate; nickel fumarate; nickelgluconate; nickel bis-glycinate; nickel sulfate; zinc acetate; zincarginate; zinc ascorbate; zinc aspartate; zinc carboxylate; zincgluconate; zinc bis-glycinate; zinc methionate; zinc oxide; zincpicolinate; and zinc sulfate. Preferably the active metal is acopper-based active metal.

The present invention further comprises a process for preparing ahydrogen sulfide scavenger composition comprising adding to a carrier anactive metal in a ratio of from about 1.0:4.0 to about 4.0:1.0. When theactive metal is not able to be suspended in the carrier, the process canfurther comprise adding to the carrier a suspension aid, which istypically present in the composition in an amount of about 0.001 wt % toabout 10.0 wt %, based on total weight of the composition, and adispersant in an amount of about 0.001 wt % to about 10.0 wt %, based ontotal weight of the composition. Preferably, the suspension aid anddispersant are added prior to adding the active metal.

The present invention is further directed towards bitumen or asphaltmodified with the hydrogen sulfide scavenger composition describedherein. In another embodiment, the present invention is directed towardsa method of reducing hydrogen sulfide emissions from bitumen or asphaltcomprising adding to the bitumen or asphalt the hydrogen sulfidescavenger composition described herein in an amount of about 0.001 wt %to about 10.0 wt %, based on total weight of the modified bitumen orasphalt, more preferably in an amount of about 0.10 wt % to about 3.0 wt%. In a further embodiment, the bitumen or asphalt has been modifiedwith PPA. When modified with PPA, the scavenger composition preferablycontains a copper-based active metal, wherein the active metal ispresent in the scavenger composition in an amount sufficient to reducehydrogen sulfide emissions from the bitumen or asphalt when heated to anamount of about 10 ppm or less. Preferably, the copper-based activemetal is present in the scavenger composition in an amount of aboutabout 40.0 to 60.0 wt %, based on total weight of the scavengercomposition.

EXAMPLES

The following scavengers were used in the Examples provided below—

TABLE 1 Scavengers Scavenger A 40% copper bisglycinate in 60% glycerolScavenger B Copper bisglycinate (powder) Scavenger C Copper Carbonatescavenger composition Scavenger D Copper carbonate (low bulk densitypowder) Scavenger E Copper carbonate (high bulk density powder)Scavenger F Zinc carboxylate in 10-30% naphtha oil Scavenger G Copper(I) oxide Scavenger H Copper (II) oxide Scavenger I Iron bisglycinateScavenger J Zinc bisglycinate ¹ Scavenger C is a scavenger compositionaccording to the invention and is comprised of a suspension media,suspension aid, dispersant and metal chelate. The active metal is coppercarbonate suspended in mineral oil (suspension media or carrier) withmodified polyolefin (suspension aid) and alkyl amine sulfonate(dispersant).

In addition to Scavenger C above, following are non-limiting examples ofother scavenger compositions according to the invention—

Scavenger Formulation Example 1

A scavenger formulation was prepared by mixing 479.8 grams (‘g’) of lowdensity copper carbonate (copper (II) hydroxide with d₅₀=2.5 microns)(active metal) with 500.02 g of glycerol (carrier), 0.201 g of xanthangum (suspension aid), and 20.07 g of sodium polysulfonate (dispersant)in a 2 liter beaker. The formulation was mixed for 60 minutes undersufficient speed to achieve a stable suspension having a Hegman gaugevalue of 6. The formulation contained about 48% by weight coppercarbonate with a viscosity of 542 cP at 66° C.

Scavenger Formulation Example 2

A scavenger formulation was prepared by charging 2571 lbs of whitemineral oil (carrier) into a mixing vessel. 39 lbs of modifiedpolyolefin (suspension aid, 25% active) and 56 lbs of alkyl aminesulfonate (dispersant) were then added to the vessel with mixing. Onceuniform, 2665 lb of copper carbonate (copper (H) carbonate hydroxide)(active metal) was added under agitation. The formulation was mixed for30 minutes and then processed in a small media mill for 180 minutesresulting in a stable suspension having a Hegman gauge value of 6.75.The formulation contained about 50% by weight copper carbonate with aviscosity of 1008 cP at 25° C.

Scavenger Formulation Example 3

A scavenger formulation was prepared by charging 2581 lbs of whitemineral oil (carrier) into a mixing vessel. 39 lbs of modifiedpolyolefin (suspension aid, 25% active) and 57.5 lbs of alkyl aminesulfonate (dispersant) were then added to the vessel with mixing. Onceuniform, 2684 lb of copper carbonate (copper (11) carbonate hydroxide)(active metal) was added under agitation. The formulation was mixed for30 minutes and then processed in a small media mill for 235 minutesresulting in a stable suspension having a Hegman gauge value of 6.5. Theformulation contained about 50% by weight copper carbonate with aviscosity of 1245 cP at 25° C.

Scavenger Formulation Example 4

A scavenger formulation was prepared by charging 2661 lbs of whitemineral oil (carrier) into a mixing vessel. 39 lbs of modifiedpolyolefin (suspension aid, 25% active) and 57.5 lbs of alkyl aminesulfonate (dispersant) were then added to the vessel with mixing. Onceuniform, 2684 lb of copper carbonate (copper (II) carbonate hydroxide)(active metal) was added under agitation. The formulation was mixed for30 minutes and then processed in a small media mill for 180 minutesresulting in a stable suspension having a Hegman gauge value of 6.75.The formulation contained about 50% by weight copper carbonate with aviscosity of 1047 cP at 25° C.

Example 1—Efficacy of Different Metal Chelates as Scavengers

various metal chelates in powder form (see Table 1 above) were comparedagainst each other as scavengers in two different sources of bitumen todetermine their efficacy in reducing H₂S emissions. The scavengers wereadded to bitumen in an amount of 0.5 wt % based on total weight of thescavenger modified bitumen after the bitumen was heated to either 160°C. or 180° C. and held at that temperature for one hour. H₂Smeasurements were taken at 5 minutes after addition and 1 hour afteraddition. The results of the efficacy of the scavengers in reducing H₂Semissions are presented in the following table—

TABLE 1 H₂S Release from Bitumen with Scavenger Added Peak H₂S H₂SEmission H₂S Emission Emission 5 minutes 60 minutes Scavenger (ppm)after addition after addition PG 64-22 I 57 17 3 Bitumen B 15 7 3 at160° C. J 25 9 5 PG 64-22 I 3 1 2 Bitumen B 2 1 2 at 180° C. J 4 2 3 PG70-22 I 5 1 4 Bitumen at B 2 1 1 160° C. J 6 2 6 PG 70-22 I 52 8 12Bitumen at B 12 4 1 180° C. J 10 5 1

The above results illustrate that for the PG 64-22 bitumen, addition ofScavengers I (iron) and B (copper) resulted in lower H₂S emissions thanScavenger J (zinc). Further, the PG 64-22 bitumen did not digestScavenger J as easily as Scavengers I and B (i.e., some of Scavenger Jconglomerated on the surface of the bitumen instead of blending into thebitumen), resulting in a less homogenous blend. For the PG 70-22bitumen, only Scavenger B was completely digested by the bitumen.Scavengers I and J were not, resulting in less homogenous blends forthese two scavengers. Scavenger B also exhibited the lowest H₂Semissions at both temperatures. These results suggest that copperfunctions as a better metal chelate in bitumen than iron or zinc.

Example 2—H₂S Analysis of Bitumen (Open System) Bitumen with Sulfur(0.005%) but without Scavenger

Bitumen with added sulfur but free of any scavenger was evaluated forhydrogen sulfide (H₂S) generation as follows. 300 g of BP PG 64-22bitumen was charged into a steel quart can equipped with a lid havingport holes for a propeller blade, thermocouple and stopcock (for H₂Smeasurements). The bitumen was heated to 160° C. while agitating at 300rpm. Once the desired temperature was reached, the bitumen was held atthat temperature for 15 minutes. Sulfur was then added to the bitumen inan amount of 0.005% by total weight of bitumen (time=0 minutes). An H₂Sreading was taken after holding at 160° C. for 15 minutes, with H₂Smeasurements continued to be taken every 10 minutes until no H₂S wasdetected. The results of the H₂S release were as follows—

TABLE 2 H₂S Release from Bitumen with sulfur additive Time (minutes) H₂SRelease (ppm) 15 380 25 100 35 100 45 5

As seen from Example 1 above, unmodified bitumen generates a low amountof H₂S emission. Therefore, in order to show the effect of the variousadditives on H₂S emission in this Example and the Examples below, sulfurwas added to generate a greater H₂S emission.

Example 3—H₂S Analysis of Bitumen (Open System) Bitumen with AddedSulfur (0.02%) but without Scavenger

Bitumen with added sulfur free of any scavenger was evaluated forhydrogen sulfide (H₂S) generation as follows. 300 g of Lion PG 64-22bitumen was charged into a steel quart can equipped with a lid havingport holes for a propeller blade, thermocouple and stopcock (for H₂Smeasurements). The bitumen was heated to 160° C. while agitating at 300rpm. Once the desired temperature was reached, sulfur was then added tothe bitumen in an amount of 0.02% by total weight of bitumen (t=0). AnH₂S reading was taken after 15 minutes, with H₂S measurements takenevery 10 minutes for a total of 90 minutes. The results of the H₂Srelease were as follows

TABLE 3 H₂S Release from Bitumen with sulfur additive Time (minutes) H₂SRelease (ppm) 15 3078 25 1758 35 1458 45 883 55 500 60 292 70 208 80 15890 98

Example 4—H₂S Analysis of Bitumen (Open System)—Bitumen with Sulfur andScavenger

Bitumen with added sulfur and scavenger was evaluated for hydrogensulfide (H₂S) generation as follows. 300 g of Lion PG 64-22 bitumen wascharged into a steel quart can equipped with a lid having port holes fora propeller blade, thermocouple and stopcock (for H₂S measurements). Thebitumen was heated to 160° C. while agitating at 300 rpm. Once thedesired temperature was reached, sulfur was then added to the bitumen inan amount of 0.02% by total weight of bitumen (t=0). After holding at160° C. for 15 minutes, an H₂S reading was taken and scavenger (letterreference provided in the Table below) was then added at 20 minutes inan amount of 0.25% by weight of total bitumen, with H₂S measurementstaken every 10 minutes for a total of 90 minutes. The results of the H₂Srelease were as follows—

TABLE 4 H₂S Release from Bitumen with sulfur and scavenger H₂S H₂S H₂SH₂S H₂S H₂S H₂S Release Release Release Release Release Release ReleaseTime (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (minutes) (C) (D) (E) (B)(F) (G) (H) 15 3078 ¹   3078 3078 3078 3078 3078 3078 25 195  20 40 90 02225 1800 35   0 ² 0 0 0 0 950 1800 45 0 0 0 0 0 195 1450 55 0 0 0 0 040 775 60 0 0 0 0 0 30 400 70 0 0 0 0 0 30 225 80 0 0 0 0 0 20 160 90 00 0 0 0 20 70 ¹ For minute 15 only, the ppm value is the average valueof all seven runs. ² “0” values in the table indicate values belowdetection level.

The above results illustrate that the addition of scavengers tounmodified bitumen results in a reduction in H₂S release from thebitumen. Further, the active copper in the slurry composition accordingto the invention (Scavenger C) is as effective as the active copperpowder (Scavengers B, D and E), although present in the bitumen in alesser amount,

Example 5 H₂S Analysis of Bitumen (Open System)—Bitumen with Sulfur, PPA& Scavenger

Bitumen with added sulfur and scavenger was evaluated for hydrogensulfide (H₂S) generation as follows. 300 g of Lion PG 64-22 bitumen wascharged into a steel quart can equipped with a lid having port holes fora propeller blade, thermocouple and stopcock (for H₂S measurements). Thebitumen was heated to 160° C. while agitating at 300 rpm. Once thedesired temperature was reached, sulfur was then added to the bitumen inan amount of 0.02% by total weight of bitumen (t=0). After holding at160° C. for 15 minutes, an H₂S reading was taken, with H₂S measurementstaken every 10 minutes for a total of 90 minutes. Scavenger (letterreference provided in the Table below) was added at minute 20 in anamount of 0.25% by weight of total bitumen. At minute 30, PPA was addedin an amount of 1.0% by weight of total bitumen. The results of the H₂Srelease were as follows—

TABLE 5 H₂S Release from Bitumen with sulfur, PPA and scavengeradditives H₂S H₂S H₂S H₂S H₂S Time Release Release Release ReleaseRelease (minutes) (ppm) (C) (ppm) (E) (ppm) (F) (ppm) (G) (ppm) (H) 151383 *   1383 1383 1383 1383 25 0 90 0 680 2000 35 0 50 2100 400 2000 450 10 775 110 1500 55 0 0 375 50 925 60 0 0 225 20 800 70 0 0 200 10 70080 0 0 190 10 425 90 0 0 180 10 375 * Average value at minute 15 of allfive runs.

The above results illustrate that the addition of PPA to bitumen withscavenger illustrates that not all scavengers are compatible with PPA inreducing H₂S emissions from the bitumen.

Example 6—H₂S Analysis of Bitumen (Open System)—Bitumen with AddedSulfur and Scavenger

Bitumen with added sulfur and scavenger was evaluated for hydrogensulfide (H₂S) generation as follows. 300 g of BP PG 58-28 bitumen wascharged into a steel quart can equipped with a lid having port holes fora propeller blade, thermocouple and stopcock (for H₂S measurements). Thebitumen was heated to 160° C. while agitating at 300 rpm. Once thedesired temperature was reached, the bitumen was held at thattemperature for 15 minutes. Sulfur was then added to the bitumen in anamount of 0.005% by total weight of bitumen (t=0). An H₂S reading wastaken after holding at 160° C. for 15 minutes, with H₂S measurementscontinued to be taken every 10 minutes until no H₂S was detected.Scavenger A was added to the bitumen in an amount of 0.4% by totalweight of bitumen with mixing at minute 20. The same process was runagain, but this time with Scavenger B instead of Scavenger A. Theresults of the H₂S release were as follows—

TABLE 6 H₂S Release from Bitumen with added sulfur and scavenger TimeH₂S Release H₂S Release (minutes) (ppm) (A) (ppm) (B) 15 520 600 25 20080 34 35 8 45 5 2

The above results illustrate that the addition of a copper-basedscavenger to bitumen modified with sulfur results in a decrease in H₂Srelease from the bitumen in both powder and dispersed form. Further, asScavenger A has only 40% active copper scavenger compared to Scavenger.B, the above data illustrates that in a dispersed form, H₂S can bereduced with less active metal, and that the dispersed form distributesthe scavenger throughout the bitumen more effectively than the powderedform.

The following Examples illustrate H₂S release from bitumen in a closedsystem. The above Examples were open systems, that is, the steel quartcan had ports. In the closed system the bitumen was sealed as describedbelow and heated in an oven.

Example 7—H₂S Analysis of Bitumen (Closed System)—Bitumen with AddedSulfur but No Scavenger

Bitumen with added sulfur was evaluated for hydrogen sulfide (H₂S)generation as follows. A one-gallon can of BP PG 64-22 bitumen washeated to fluidity at about 177° C., and then 3298.35 g of the fluidbitumen was then poured into another can. This sample was heated to 180°C. under low shear. Once 180° C. was reached, 1.65 g of sulfur (0.05 wt%) was added for a total mixture of 3300 g, and mixed for 60 minuteswhile maintaining the temperature. This blend was then charged intoseparate steel quart cans in amounts of 500 g each (with one only having300 g). Each quart can was capped (closed system) and then heated forabout 24 hours at fluidity at about 177° C. in an oven. One can was thenpunctured and an H₂S measurement taken. The H₂S reading showed a releaseof 60,000 ppm H₂S from the sulfur-modified bitumen. NOTE: An H₂S readingof unmodified bitumen (i.e., without sulfur) only showed a nominalrelease of H₂S. Sulfur was therefore added in the Examples toartificially generate a measureable amount of H₂S in order todemonstrate scavenger efficacy.

Example 8—H₂S Analysis of Bitumen (Closed System)—Bitumen with AddedSulfur and PPA but No Scavenger

Bitumen with added sulfur and PPA was evaluated for hydrogen sulfide(H₂S) generation as follows. A one-gallon can of BP PG 64-22 bitumen washeated to fluidity at about 177° C., and then 3281.85 g of the fluidbitumen was then poured into another can. This sample was heated to 180°C. under low shear. Once 180° C. was reached, 1.65 g of sulfur (0.05 wt%) was added and mixed for 30 minutes while maintaining the temperature.16.5 g of PPA (0.50 wt %) was then added for a total mixture of 3300 g,and mixed for an additional 30 minutes while maintaining temperature.This blend was then charged into separate steel quart cans in amounts of500 g each (with one only having 300 g). Each quart can was capped(closed system) and then heated to fluidity at about 177° C. in an ovenand held at that temperature for 24 hours. One can was then puncturedand an H₂S measurement taken. The H₂S reading showed a release of105,000 ppm H₂S from the sulfur and PPA-modified bitumen, indicatingthat addition of PPA increases the amount of H₂S released.

Example 9—H₂S Analysis of Bitumen (Closed System)—Bitumen with AddedSulfur and Polymer but No Scavenger

Bitumen with added sulfur and polymer was evaluated for hydrogen sulfide(H₂S) generation as follows. A one-gallon can of BP PG 64-22 bitumen washeated to fluidity at about 177° C. and then 3199.35 g of the fluidbitumen was then poured into another can. This sample was heated to 180°C. under high shear (3000-4000 rpm). Once 180° C. was reached, 99.00 gof SBS (3.0 wt % styrene-butadiene-styrene) polymer was added and mixedfor 180 minutes at high shear while maintaining the temperature. 1.65 gof sulfur (0.05 wt %) was then added for a total mixture of 3300 g, andmixed for an additional 60 minutes at medium shear (2000 rpm) whilemaintaining temperature. This blend was then charged into separate steelquart cans in amounts of 500 g each (with one only having 300 g). Eachquart can was capped (closed system) and then heated to fluidity atabout 177° C. in an oven for 24 hours. One can was then punctured and anH₂S measurement taken. The H₂S reading showed a release of 31,000 ppmH₂S from the sulfur and polymer-modified bitumen.

Example 10—H₂S Analysis of Bitumen (Closed System)—Bitumen with AddedPolymer, Sulfur and PPA but No Scavenger

Bitumen with added polymer, sulfur and PPA was evaluated for hydrogensulfide (H₂S) generation as follows. A one-gallon can of BP PG 64-22bitumen was heated to fluidity at about 177° C., and then 3182.85 g ofthe fluid bitumen was then poured into another can. This sample washeated to 180° C. under high shear (3000-4000 rpm). Once 180° C. wasreached, 99.00 g of SBS (3.0 wt % styrene-butadiene-styrene) polymer wasadded and mixed for 180 minutes at high shear while maintaining thetemperature. 1.65 g of sulfur (0.05 wt %) was then added and mixed foran additional 30 minutes at medium shear (2000 rpm) while maintainingtemperature. 16.5 g of PPA (0.50 wt %) was then added and mixed for anadditional 30 minutes at medium shear (2000 rpm) while maintainingtemperature. This blend was then charged into separate steel quart cansin amounts of 500 g each (with one only having 300 g). Each quart canwas capped (closed system) and then heated to fluidity at about 177° C.in an oven and held there for 24 hours. The cans were removed from theoven and one can was then punctured and an H₂S measurement taken. TheH₂S reading showed a release of 13,000 ppm H₂S from the polymer, sulfurand PPA-modified bitumen.

The following Examples illustrate the effect of the addition ofscavenger to the four closed systems described above.

Example 11—H₂S Analysis of Bitumen (Closed System)—Bitumen with AddedSulfur and Scavenger

Bitumen with added sulfur and two different scavengers was evaluated forhydrogen sulfide (H₂S) generation as follows. Two separate one-galloncans of BP PG 64-22 bitumen were heated to fluidity at about 177° C.,and then 3298.35 g of the fluid bitumen was then poured into anothercan. The samples were heated to 180° C. under low shear. Once 180° C.was reached, 1.65 g of sulfur (0.05 wt %) was added to each sample for atotal mixture of 3300 g, and mixed for 60 minutes while maintaining thetemperature. The 3300 g blends were then charged into separate steelquart cans in amounts of 500 g each (with two only having 300 g). Eachquart can was capped (closed system) and then re-heated for about 20minutes to fluidity at about 177° C. equipped in an oven. Four cans wereremoved from the oven and injected with one scavenger as follows

TABLE 7 Bitumen with added sulfur and scavenger Blend Scavenger type andamount PG 64-22 + 0.05% Sulfur 0.125 wt % Scavenger C 0.250 wt %Scavenger C 0.125 wt % Scavenger F 0.250 wt % Scavenger F

The cans were then tumbled for about 10 minutes for mixing, and thenplaced back in the oven for 24 hours at 177° C. Each can was thenpunctured and an H₂S measurement taken. The H₂S results were as follows—

TABLE 8 H₂S Release from Bitumen with added sulfur and scavenger BlendScavenger type and amount H₂S (ppm) PG 64-22 + 0.05% None (Ex. 11 above)60,000 Sulfur 0.125 wt % Scavenger C 15,000 0.250 wt % Scavenger C toolow to detect 0.125 wt % Scavenger F 13,000 0.250 wt % Scavenger F toolow to detect

The above results illustrate that different scavengers can reduce theamount of H₂S released from bitumen.

Example 12—H₂S Analysis of Bitumen (Closed System)—Bitumen with AddedSulfur, PPA and Scavenger

Bitumen with added sulfur, PPA and two different scavengers wasevaluated for hydrogen sulfide (H₂S) generation as follows. Two separateone-gallon cans of BP PG 64-22 bitumen were heated to fluidity at about177° C., and then 3281.85 g of the fluid bitumen was then poured intoanother can. This sample was heated to 180° C. under low shear. Once180° C. was reached, 1.65 g of sulfur (0.05 wt %) was added and mixedfor 30 minutes while maintaining the temperature. 16.5 g of PPA (0.50 wt%) was then added for a total mixture of 3300 g, and mixed for anadditional 30 minutes while maintaining temperature. The 3300 g blendswere then charged into separate steel quart cans in amounts of 500 geach (with two only having 300 g). Each quart can was capped (closedsystem) and then re-heated for about 20 minutes to fluidity at about177° C. equipped in an oven. Four cans were removed from the oven andinjected with one scavenger as follows

TABLE 9 Bitumen with added sulfur, PPA and scavenger Blend Scavengertype and amount PG 64-22 + 0.05% Sulfur + 0.125 wt % Scavenger C 0.50%PPA 0.250 wt % Scavenger C 0.125 wt % Scavenger F 0.250 wt % Scavenger F

The cans were then tumbled for about 10 minutes for mixing, and thenplaced back in the oven for 24 hours at 177° C. Each can was thenpunctured and an H₂S measurement taken. The H₂S results were as follows

TABLE 10 H₂S Release from Bitumen with added sulfur, PPA and scavengerBlend Scavenger type and amount H₂S (ppm) PG 64-22 + 0.05% None (Ex. 12above) 105,000 Sulfur + 0.50% PPA 0.125 wt % Scavenger C 7,500 0.250 wt% Scavenger C 700 0.125 wt % Scavenger F 90,000 0.250 wt % Scavenger F85,000

The above results illustrate that Scavenger C (according to the presentinvention) can reduce the amount of H₂S released from bitumen whenmodified with PPA and sulfur, whereas a commercially available ScavengerF cannot.

Example 13—H₂S Analysis of Bitumen (Closed System)—Bitumen with AddedPolymer, Sulfur and Scavenger

Bitumen with added polymer, sulfur and Scavenger C was evaluated forhydrogen sulfide (H₂S) generation as follows. A one-gallon can of BP PG64-22 bitumen was heated to fluidity at about 177° C., and 3199.35 g ofthe fluid bitumen was then poured into another can. This sample washeated to 180° C. under high shear (3000-4000 rpm). Once 180° C. wasreached, 99.00 g of SBS (3.0 wt % styrene-butadiene-styrene) polymer wasadded and mixed for 180 minutes at high shear while maintaining thetemperature. 1.65 g of sulfur (0.05 wt %) was then added for a totalmixture of 3300 g, and mixed for an additional 60 minutes at mediumshear (2000 rpm) while maintaining temperature. The 3300 g blends werethen charged into separate steel quart cans in amounts of 500 g each(with one only having 300 g). Each quart can was capped (closed system)and then re-heated for about 20 minutes to fluidity at about 177° C.equipped in an oven. Two cans were removed from the oven and injectedwith Scavenger C as follows—

TABLE 11 Bitumen with added sulfur, polymer and scavenger BlendScavenger type and amount PG 64-22 + 3.00% SBS + 0.125 wt % Scavenger C0.05% Sulfur 0.250 wt % Scavenger C

The cans were then tumbled for about 10 minutes for mixing, and thenplaced back in the oven for 24 hours at 177° C. Each scavenger added canwas then punctured and an H₂S measurement taken. The H₂S results were asfollows—

TABLE 12 H₂S Release from Bitumen with added sulfur, polymer andscavenger Blend Scavenger type and amount H₂S (ppm) PG 64-22 + 3.00%None (Ex. 13 above) 31,000 SBS + 0.05% Sulfur 0.125 wt % Scavenger C2,000 0.250 wt % Scavenger C too low to detect

The above results illustrate that Scavenger C (according to the presentinvention) can reduce the amount of H₂S released from bitumen whenmodified with polymer crosslinked with sulfur.

Example 14—H₂S Analysis of Bitumen (Closed System)—Bitumen with AddedPolymer, Sulfur, PPA and Scavenger

Bitumen with added polymer, sulfur, PPA and Scavenger C was evaluatedfor hydrogen sulfide (H₂S) generation as follows. A one-gallon can of BPPG 64-22 bitumen was heated to fluidity at about 177° C., and then3182.85 g of the fluid bitumen was then poured into another can. Thissample was heated to 180° C. under high shear (3000-4000 rpm). Once 180°C. was reached, 99.00 g of SBS (3.0 wt % styrene-butadiene-styrene)polymer was added and mixed for 180 minutes at high shear whilemaintaining the temperature. 1.65 g of sulfur (0.05 wt %) was then addedand mixed for an additional 60 minutes at medium shear (2000 rpm) whilemaintaining temperature. 16.5 g of PPA (0.50 wt %) was then added andmixed for an additional 30 minutes at medium shear (2000 rpm) whilemaintaining temperature. The 3300 g blends were then charged intoseparate steel quart cans in amounts of 500 g each (with two only having300 g). Each quart can was capped (closed system) and then re-heated forabout 20 minutes to fluidity at about 177° C. equipped in an oven. Two500 g cans were removed from the oven and injected with Scavenger C asfollows—

TABLE 13 Bitumen with added sulfur, polymer, PPA and scavenger BlendScavenger type and amount PG 64-22 + 3.00% SBS + 0.125 wt % Scavenger C0.05% Sulfur + 0.50% PPA 0.250 wt % Scavenger C

The cans were then tumbled for about 10 minutes for mixing, and thenplaced back in the oven for 24 hours at 177° C. Each can was thenpunctured and an H₂S measurement taken. The H₂S results were as follows—

TABLE 14 H₂S Release from Bitumen with added sulfur, polymer, PPA andscavenger Blend Scavenger type and amount H₂S (ppm) PG 64-22 + 3.00%SBS + None (Ex. 14 above) 13,000 0.05% Sulfur + 0.50% PPA 0.125 wt %Scavenger C 9,800 0.250 wt % Scavenger C 1,400

The above results illustrate that Scavenger C (according to the presentinvention) can reduce the amount of H₂S released from bitumen whenmodified with crosslinked polymer and PPA.

The scavenger composition according to the present invention asdescribed above affords several advantages over powdered scavengers.These include (a) ease of metering into bitumen or asphalt, as a liquidscavenger composition is easier to meter than a powdered one; (b)elimination or reduction of dust potential; (c) the ability to injectthe liquid composition to counter pressure build-up in piping, asliquids are substantially non-compressible; and (d) as previously noted,the compatibility of the copper salt or chelate component with PPA.

The above description discloses several methods and materials of thepresent invention. This invention is susceptible to modifications in themethods and materials, as well as alterations in the fabrication methodsand equipment. Such modifications will become apparent to those skilledin the art from a consideration of this disclosure or practice of theinvention disclosed herein. Consequently, it is not intended that thisinvention be limited to the specific embodiments disclosed herein, butthat it cover all modifications and alternatives coming within the truescope and spirit of the invention as embodied in the attached claims.

We claim:
 1. A scavenger composition for reducing hydrogen sulfideemissions from asphalt comprising: a carrier in an amount of about 1.0wt % to about 99.0 wt. %, based on total weight of the composition, adispersant in an amount of about 0.01 wt % to about 10.0 wt. %, based ontotal weight of the composition, and an active metal in an amount ofabout 99.0 wt % to about 1.0 wt. %, based on total weight of thecomposition, wherein the dispersant is chosen from sodium acidpyrophosphate, sodium polysulfonate, sodium alkyl sulfosuccinate, soylecithin, hydroxyl-functional carboxylic acid esters, salts ofunsaturated polyamine amides and lower molecular weight acidicpolyesters, and alkyl amine sulfonates, and wherein the active metal isa metal salt or metal chelate, and wherein the metal is chosen fromiron, copper, molybdenum, nickel and zinc.
 2. The scavenger compositionaccording to claim 1 further comprising: a suspension aid.
 3. Thescavenger composition according to claim 2 wherein the suspension aid ispresent in an amount of about 0.01 wt % to about 10.0 wt. %, based ontotal weight of the composition.
 4. The scavenger composition accordingto claim 1 wherein the active metal is about 100 microns or less indiameter.
 5. The scavenger composition according to claim 1 wherein theactive metal is chosen from copper aspartate; copper carbonate; coppercitrate; copper gluconate; copper bis-glycinate; copper oxides; copperoxalate; copper sulfate; iron aspartate; iron bis-glycine; iron citrate;iron fumarate; iron gluconate; iron bis-glycinate; iron sulfate;molybdenum aspartate; molybdenum bis-glycine; molybdenum citrate;molybdenum fumarate; molybdenum gluconate; molybdenum glycinate;molybdenum sulfate; nickel aspartate; nickel bis-glycine; nickelcitrate; nickel fumarate; nickel gluconate; nickel bis-glycinate; nickelsulfate; zinc acetate; zinc arginate; zinc ascorbate; zinc aspartate;zinc carboxylate; zinc gluconate; zinc bis-glycinate; zinc methionate;zinc oxide; zinc picolinate; and zinc sulfate.
 6. The scavengercomposition according to claim 1 wherein the active metal is acopper-based active metal.
 7. Bitumen or asphalt comprising thescavenger composition according to claim
 1. 8. Bitumen or asphaltaccording to claim 7, wherein the bitumen or asphalt is further modifiedwith polyphosphoric acid and the active metal is a copper-based activemetal.
 9. Bitumen or asphalt according to claim 8, wherein hydrogensulfide emissions from the bitumen or asphalt when heated to 100° C. orgreater are about 10 ppm or less.
 10. The scavenger compositionaccording to claim 2 wherein the suspension aid is chosen frompolysaccharides, fumed silica, modified bentonite, hectorites, castoroil derivatives, polyamides, polyolefins, and polyacrylates.
 11. Thescavenger composition according to claim 5, wherein the active metal ischosen from copper aspartate; copper carbonate; copper citrate; coppergluconate; copper bis-glycinate; copper oxides; copper oxalate; andcopper sulfate.
 12. The scavenger composition according to claim 1,wherein the carrier is chosen from glycerol, polypropylene glycol,polyethylene glycol, white mineral oil, mineral spirits, hydrotreatedlight petroleum distillate, white spirits, Stoddard solvent, aliphaticnaphtha, and hydrotreated heavy petroleum distillate.
 13. A method ofreducing hydrogen sulfide emissions from asphalt or bitumen comprisingadding to the asphalt or bitumen a scavenger composition comprising: acarrier present in an amount of about 1.0 wt % to about 99.0 wt. %,based on total weight of the composition, a dispersant present in anamount of about 0.01 wt % to about 10.0 wt. %, based on total weight ofthe composition, wherein the dispersant is chosen from sodium acidpyrophosphate, sodium polysulfonate, sodium alkyl sulfosuccinate, soylecithin, hydroxyl-functional carboxylic acid esters, salts ofunsaturated polyamine amides and lower molecular weight acidicpolyesters, and alkyl amine sulfonates, and an active metal present inan amount of about 99.0 wt % to about 1.0 wt. %, based on total weightof the composition, wherein the active metal is a metal salt or metalchelate, and wherein the metal is chosen from iron, copper, molybdenum,nickel, and zinc.
 14. The method according to claim 13, wherein thescavenger composition further comprises a suspension aid.
 15. The methodaccording to claim 14, wherein the suspension aid is present in anamount of about 0.01 wt % to about 10.0 wt %, based on total weight ofthe composition.
 16. The method according to claim 13, wherein thebitumen or asphalt is further modified with polyphosphoric acid and theactive metal is a copper-based active metal.
 17. A scavenger compositionfor reducing hydrogen sulfide emissions from asphalt comprising: acarrier in an amount of about 1.0 wt % to about 99.0 wt. %, based ontotal weight of the composition, wherein the carrier is chosen fromglycerol, polypropylene glycol, polyethylene glycol, white mineral oil,mineral spirits, hydrotreated light petroleum distillate, white spirits,Stoddard solvent, aliphatic naphtha, hydrotreated heavy petroleumdistillate, and combinations thereof, an active metal in an amount ofabout 99.0 wt % to about 1.0 wt. %, based on total weight of thecomposition, wherein the active metal is a metal salt or metal chelate,and wherein the metal is chosen from iron, copper, molybdenum, nickel,and zinc, and a suspension aid in an amount of about 0.01 wt % to about10.0 wt. %, based on total weight of the composition, wherein thesuspension aid is chosen from polysaccharides, fumed silica, modifiedbentonite, hectorites, castor oil derivatives, polyamides, polyolefins,polyacrylates, and combinations thereof.
 18. The scavenger compositionaccording to claim 17, wherein the active metal is a particle or powderhaving a diameter of about 100 microns or less.